Hold Shared Sandbox Work Behind a Promotion Lane

Shared free compute is not a merge queue. Agent output on a borrowed server still needs a named owner. A sealed replay kit must exist before anyone ships. A human stamp still sits between sandbox and repo. Teams skip that gate when a sandbox feels disposable. Disposable hardware is the point of the machine. Disposable patches are not the point of shipping. The next person inherits a dirty shared desk. Last run guesses then leak into the next ticket. A hotel room remains the right working analogy. Guests may boil water in the kettle. They should not leave soup on the stove. Checkout is an inspection and not a feeling. Shared agent sandboxes need that same checkout. Public talk about smarter agents stays loud. The floor problem is duller than model rankings. The loop can look healthy while the room rots. Two operators may share one login and disk. Green tests then belong to the previous tenant. An agent can look busy on a shared box. Files appear in odd folders without owners. Tests can flicker green only one time. Nobody can replay the prompt two days later. The branch name is often just tmp. The env file still holds a personal token. Loop writeups often skip this messy floor. The retry policy is not the only failure. The shared room is the quieter failure. Without a lane, every retry overwrites the last retry. Without a promotion card, sandbox luck becomes a ship argument. This playbook treats the sandbox as a hotel room. Work parks in a named lane until review. Output leaves only through a written gate. The wiki card below is the whole run. Four roles keep the hotel room honest. One person may wear two hats today. Blank names are not allowed on the card. The lane claimant books the sandbox slot. The agent operator runs the model session. The promotion reviewer refuses or stamps the patch. The lane resetter wipes the room for the next guest. Handoffs should move in one direction only. Claim, operate, seal, and review stay ordered. Promote or scrap follows the review